Certain quaternary ammonium compounds (“QACs” or “quats”) are known for their bactericidal and fungicidal activity, especially on hard surfaces. Benzalkonium chloride (BAC) is one of the most widely used biocides used in the market. Benzalkonium chloride is the generic name (by the Official United States Pharmacopia) for a pharmaceutical aid. The USP specification indicates that 70% minimum of the total alkylbenzyldimethyl ammonium chloride contents are C12/C14 homologues. The number of homologues that were evaluated to get to that combination of molecules required an incredible amount of work and research time, and that was just the first generation of QACs. Modification of the benzene ring with different alkyl and halide groups led to a second generation of substituted benzalkonium chlorides. A third generation resulted from the evaluation of dialkyldimethylammonium chlorides. These were by far of the greatest commercial significance. The fourth generation of quaternary ammonium compounds was brought on in 1965 by a technological breakthrough. Catalytic amination of long chain alcohols made possible the production of dialkylmethylamines, which react with methylchloride to make twin chain quaternary ammonium compounds such as didecyldimethylamonium chloride and dioctadecylydimethyl ammonium chloride. Research then branched in other directions, such as using N-laurylpyridinium and blends of different generations of quats. The fourth generation quats products showed an outstanding bactericidal performance, good tolerance for anionic surfactants, proteins loads, hard water and did not cause as many foam problems.1 (Ref R)
QACs are primarily active against Gram-positive bacteria, whereas in agriculture almost all of the significant bacterial diseases are Gram-negative. At higher concentrations, quats are bactericidal towards Gram-negative bacteria, but some strains are quite resistant. Viruses are even more resistant, even though certain quats exhibit virucidal activity against many lipophilic viruses.(Ref S). Bond in 1995 (Ref S) suggested that a crucial aspect of quats' activity against HIV and the hepatitis B virus (HBV) was due to the absence of organic matter. As agriculture is full of organic matter, Bond would seem to suggest that quats are relatively inactive against viruses in agriculture. Quats are also known to be fungistatic, and not fungicidal (Ref S).
QACs are known to be incompatible with a wide range of chemical compounds, including anionic surfactants, and nonionic surfactants such as lubrols, tweens, and phospholipids such as lecithin found in soybean oil and other fat containing materials.(Ref S) Smolka did report that some QACs can be activated by nonionic surfactants. The antimicrobial activity of the QACs is greatly altered by organic matter, including milk, serum, and feces, which reduce their activity.
QACs are used in food hygiene, in hospitals, as a soak for hard contact lenses, and some are used to treat small wound surfaces, shampoos, and cosmetics. They have been used in the veterinary field to clean and disinfect automatic calf feeders, and in sheep dips, but they are not used in large amounts on farms, presumably due to the organic debris they are going to encounter (Ref S). In general, QACs are effective preservatives for pharmaceuticals and disinfectants for hard surfaces.
However, efficacy studies (Ref 1, 2) suggest considerable differences between BACs and other known QACs. On Staphylococcus, BACs are about 2.5 as effective as other QACs tested. On contact lenses they are about 6 times as effective. They are primarily active against gram-positive bacteria. They are also fungistatic and not fungicidal. The activity of QACs is affected greatly by organic matter. They are used for contact lenses, skin disinfection, deodorants, shampoos, and controlling algae in swimming pools. There are products on the market based on BAC used for controlling bacteria and fungus on turf and ornamental plants, but problems with phytotoxicity and environmental concerns have kept it from being used in agriculture. QACs are phytotoxic and many are cytotoxic as well. BAC is over 100 times as cytotoxic as other QACs, so there can be large differences in not only activity, but cell death from different QACs.
It would be advantageous to develop quaternary ammonium compounds other than BACs which are microbiocidally effective against the type of microbes present in agriculture, and which do not lose their potency in the presence of organic matter, such as that present in agriculture. The present invention provides such quaternary ammonium compounds, and methods of treating crops, plants, swimming pools and the like using the compounds.